Fairly recently developed thermally insulated concrete building blocks are being used more frequently in construction. This form of building block combines the advantages of concrete block construction with "built in" thermal insulation properties. The new blocks use layers of rigid foam insulation situated within each block.
The insulation layer is positioned along one side wall of an opening passing through the block. The insulation is fragile and can easily loose its insulative properties if damaged. Extreme care must be taken in handling the blocks to avoid damage to the insulation material. This creates a problem in handling, especially since the insulation layer is usually situated within the block in such a manner that the remainder of the internal block opening is offset. The block can be handled effectively only from sides of the opening clear of the insulation or from outside surfaces if they are to be handled manually.
Manual handling of insulated concrete blocks is difficult for the reason that the blocks are large and heavy and for the fact that they are very awkward to handle due to the placement of the insulation against one of the interior block walls. The blocks therefore require so much added caution by the masons and helpers that installation costs are increased dramatically over standard concrete block construction.
The above problem with increased labor costs, added to the increased costs of the insulated blocks themselves, has often discouraged builders from taking advantage of the rather remarkable insulative properties of this form of block construction.
Attempts have been made to solve the above problem by developing mechanical grabs for handling the blocks.
In confronting general blcok handling problems set forth above, several designs have been developed for use in gripping building blocks from the outside surfaces. For example, U.S. Pat. No. 2,657,571 to Looze, granted in 1953 for a concrete block handling discloses a mechanism by which outside surfaces of concrete blocks are gripped for placement in a wall structure. A somewhat similar arrangement is disclosed in a 1908 U.S. Pat. No. 905,010 to Simmons. Simmons discloses a toggle-actuated grapple for lifting and handling concrete blocks. Both forms of the external grab arrangements have inherent disadvantages. Often, concrete blocks are stacked with external surfaces in abutment with one another. This severely limits access for contact by external gripping mechanisms. Furthermore, external gripping mechanisms often hinder handling of the blocks in situations where there is limited space for the mason or for placement of the block.
Another attempted solution involves grapple or grab apparatus that includes internal mechanisms for engaging and securing the block. Representative of an internal grap mechanism is U.S. Pat. No. 4,223,935 to Rayner et al granted in 1980 for a tool used for lifting building blocks. The tool includes a pair of handles and a block gripping mechanism designed to expand and clamp against internal walls of the block as the handles are manually gripped and lifted. The device includes an abutment surface for engaging a top side of the block and gripping members that extend into an opening within the block from the abutment surface. One of the gripping members is pivoted by a lever mechanism including a hand grip which, when lifted, causes the pivoted member to swing outwardly against a wall of the block. The gripping members are normally parallel to one another and perpendicular to the block engaging abutment surface when in a non-gripping, closed orientation. The gripping members are received within the block recess such that the stationary member will rest flush against a wall surface of the block. The pivoted membermust then be pivoted by action of the lever mechanism from its closed position to an angled, open position for engaging the block at a point or relatively small wall surface area. In another embodiment both members pivot outwardly from outward angled positions so both walls of the block are engaged along small surface areas.
Another internal gripping mechanism is exemplified by U.S. Pat. No. 1,359,649 to Allison issued in 1920 for a lifting device for glass battery jars. Allison includes spring loaded gripping members that operate from a toggle mechanism to internally engage glass battery jars. The members are normally urged to an outward gripping orientation and the toggle mechanism is used to forceably pull the gripping members inwardly to facilitate insertion and removal of the gripping members from open ended glass battery jars.
The above and other forms of gripping devices recognize the need to obtain some form of gripping device that will facilitate one hand handling of building blocks and the like. However, none recognize the problem of using such devices with thermally insulated building blocks. The problem thus remains of adequately handling insulated blocks without endangering the relatively fragile thermal insulation layer.
Some prior gripping devices, such as the Rayner device, have been used with such blocks with only limited success. There has been no provision included to adequately position the gripping members within the block clear of the insulation layer and at a position that substantially centers the gripping handle over the center of weight for the block. Special care must be taken with such forms of gripping apparatus to appropriately position the gripping members within the block in order to avoid damage to the insulation layer. Care must also be taken to properly position the grip so the load will be fairly well balanced. The time required to accomplish this end result often makes use of the tool uneconomical.
A need has therefore remained for a gripping device that includes the capability to position gripping members within the block, safely gripping the block while avoiding the internal insulation layers and simultaneously positioning the handle in relation to the block such that the bulk of the block weight is borne directly below a handle.